Telephony



TELEPHONY mma Feb, 27, 1915 5 Sheets-Sheet l Apr. 117, 1923.

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l arrow/1% Cil Patented Apr. l', 1923.

Ul'lED STATES lidildt FFME..

TELEPHONY.

Application filed February 27, 1915. Serial No. 11,046'.

To all whomvz't may concern.'

yBe it known that l, HUBERT S. TURNER, a citizen of the United States, residing at San Diego, in the county ot San Diego and State of California-have invented certain new and useful Improvements in Telephony, @t which the following is a specification.

This invention relates to telephone expichange systems, some features thereoit' being o'liparticular service in connection with switchboard systems of the central energy multiple type, vto which, however, the invention is not to be restricted, and in some of its aspects constitutes improvements on teatures ot' a telephone system disclosed :in my U. Sf Patent No. 1,128,262, granted Feb-` ruary 9, 1915.

`The lpresent invention has `for its broad objects the provision of means whereby the necessity tor the linger Contact devicey and special calling plug contact disclosed in the 'aforementioned application, is done away with; adaption of' the automatic ringing system disclosed in said application to party line ringing; the provision of improved means of selectively ringingcall bells on party lines; the provision of improved means ot operatingr supervisory signals, whereby a. plurality @t signals are produced 0 b5" *L leSSGI number of lamps; the provision ot' improved means ot obtaining a waiting connection with a' busy line; the provision ot' improved means for preventing a telephonie connection to a busy line; the provision ot automatic supervision, whereby such supervision is performed by a special supervisory operator. Other objects will be apparent from the specification.

lu order to more fully describe my inroation, reference will be had to the accompanying drawings forming a part of this specilication and wherein,

Figure 1 a diagram illustrating in. one form the various features ot my invention above mentioned; f

Figure 2 a modification ot the calling link connector shown in Figure 1;

Figure 3 a modification of the party line ringing interrupters shown in Figure 1;

Figure 4 a diagram illustrating principally a modification in which the fiuictions of the operators relay and the controlling relay illustrated in Figure 1, are combined in one relay; y y

Figure 5 a diagram showing in modied form certain features ot' my invention, illustrated in Figure l, and in addition thereto means for effecting a delayed release of the operators relay;

Figure 6 a diagram. showing a modified way of obtaining the delayed release of the operators relay, substituting a plug seat switch for the controlling` .relay shown in Figure 5;

Figure 7 a diagram illustrating a form oi my invention wherein means are provided whereby a special operator attends to the supervision of the telephonie connections established by the link connectors;

.Figure 8 a diagram illustrating a special cord circuit to be used by the special operator mentioned in connection with Figure 7 Figure 9 a diagram illustrating a modi-` tication of my invention wherein the supervisory lamps are operated in a different way to those shown in the preceding figures;

Figure 10 a diagram illustrating a modiiication ot my invention wherein but one supervisory lamp or signal is used which is displayed when the established connection is to be taken down;

Figure 11 a diagram illustrating a manually operated means Jfor energizing the operators relay illustrated in the preceding figures and an elapsed time mechanism tor fle-energizing the same.

Figure 12 al diagram illustrating an apparatus tor obtaining the disconnection of the operators telephone set trom a calling line previous to the connection being completed through to the called'line.

Figure 13 a diagram'illustrating an arrangement ot circuits and apparatus whereby the described system is adapted to trunk line operation;

Figure 14 a. diagram' illustrating a Yform ot busy test apparatus used with the circuits shown in Figures 13 and 15;

Y Figures 15 16 and 17 diafrranis illustrat-` in .Q rarious embodiments oi" my intention adapted to a trunling systems:

Figure 1S a diagram illustrating a modication or" my invention wherein the link connector shown isused for connectinga calling party to atrunlr line only;

Figure 19 afdiagram illustrating a modi- Heat-ion of the trunlting adaptation specially adapted to be used with the link' connector shown in Figure 18, but which may be used with the other link connectors illustrated in the preceding gures.

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(i ll Referring first to Figure 1, 1 represents a telephone sub-station which includes a telephone receiver 2, a transmitter 3, a switch-hook 4, a call bell 5, a condenser 6, and primary 7 and secondary 8 ot an induction coil. The elements 3 and 7 are included in a bridge ofthe telephone line, which bridge is open when the telephone receiver is upon the switch-hook 4 and which bridge is closed by the switch-hook 4, when relieved of the weight of the telephone receiver. The elements 5 and 6 are included in another bridge pern'ianently continuous with respect to alternating current, but non-continuous with respect to direct currents. The type of sub-station outfit shown is one that I have selected for the purpose of illustrating the invention. but it is to be understood that I do not limit myself to the form of sub-stations apparatus shown, iorit will be seen as the description oi the invention is proceeded with, that the operation of the system does not depend upon the peculiar sub-station outfit shown. Sub-sta tion v1 is connected. to the exchange in the form of the vinvention shown by means of metallic circuits, whose limbs 9 and 10 are connected with the line springs or talking contacts or' spring jacks 11 and 12. A, plurality oi spring jacks is shown in multiple relation with each line, the lowermost spring jack 12 constituting the answering jack., while the remaining jacks 11 constitute multiple jacks. The limbs 9 and 10 also terminate'in contacts on the right and le'l't armature switches of cutoff relay 13, the limbs of each telephone line being normally connected by means of said armature switches and the contacts normally engaged thereby with a line relay 14, the limb. 9 being connected with` the left hand winding and the limb being connected with the right hand winding of said relay, the other terminals et the windings of said relay being connected through grounded battery 15. Line relay 14 is actuated by the removal of the telephone receiver at sub-station 1 from its supporting switch-hook by means of a circuit which may be traced as follows: irom ytransinittei" 3, through line 9, left hand armature switch and normal Contact of `cut-of'relay 13, left hand winding of line relay 14 to the live pole of grounded battery 15, through said battery to ground, through resistance 16, the right hand winding of line relay 14, right hand normal contact and armature switch of cut-off relay 13, line 10, primary 7, switch-hook 4, completing the circuit through transmitter 3.- This actuation of line relay 14'causes its armature switch to close a circuit through line lamp or signal 17 which may be traced from ground through said resistance 16, said armatureswitch and engagedcontact or" line relay 14,said linelamp or signal, interrupter 18rfand itsxbrush'fand.

grounded battery 15 to ground, thus conipleting the circuit.k

Interrupter 18 consists of a rotating metallic member with one or more insulating segments, there being a shunt circuit around said interrupter through resistance 19. Hence the current passing through resistance 16 from line lamp or signal 17 is a variable one though not intermittent and the current from grounded battery 15 passing through the same resistance to the described line circuit including primary 7 is also made variable thereby. This variable current sets up an alternating current in secondary 8 which is heard as an audible signal in telephone receiver 2 which is in circuit with said secondary. It will be seen that if the circuit was open through limbs 9 and 10 there would be no path for the described variable current and hence no audible signal would be produced; and if the circuitv was open through line lamp or signal. 17 the current passing through resistance 1G would not be a variable one and again no audible signal would be produced. Therefore, the production ot said audible signal in said receiver 2 is an assurance to the party at substation 1 that the line wires are in working condition and that the line lamp or signal at the central exchangehas .been displayed.

Having observed the displayed line sig# nal of the calling sub-station the operator inserts answering plug. 20 into answering jaclr 12 corresponding to the callingsub-station. This action. closes a circuit which may be traced it'ollows: Ytrom the grounded' terminal ot' cut-off relay 13, through the winding ot said relay, sleeve of answering` jack 12, sleeve contact of answering plug 20, left hand winding of answering supervisory relay E21, windingolf operators relay 22, contact and armature switch of controlling relay 23 to the lire pole of grounded battery 15, completing the circuit through the same. rlhe actuation ot cut-off relay 13, due to the current flowing through this traced circuit breaks the circuit from substation l through line relay 14 and line lamp or signal 17 therefore resumes its nor` mal condition due to the consequent disengagement of the armature switch ot line relay 14 from its contact.

The actuation oil operators relay 22, due to the current flowing through thel same traced circuit, causes its various armature switches to be attracted.

The actuation oit answering' supervisory relay 91, due to the current iiowing. through the saine traced circuit, closes another circuit which may vbev traced as follows: from ground through battery 15, talking i interrupter 24, alternate contact and -armature switch of actuated answering .supervisory relay 21, winding of answering relay 95, sleeif'c; conta ct o-tanswering'pilug 20," sleeve. ei

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operator may be dispensed with.

answering jack l2. and winding,r of cut-oil' relay 13, completing the circuit to ground. The actuation of answering` relay 25, due to the current flowing through the circuit just traced causes its various armature switches to be attracted.

A circuit therefore may be traced as 'follows: 'trom ground through repeating coil winding 26, uppermost armature switch and engaged contact oit the two top ones of answ ringV relay 25, ring contact of answering plug- 20, ring' ycontact spring of answering jack '1.2, limb 9, transmitter 3, switch-hook l, primary 7, limb l0, tip spring of answering jaclr l2, tip Contact of answering plug 20, right hand winding of answering supervisory relay 2l and the nen-inductive resistance in multiple relation thereto, lowermost engaged contact and armature switch of the three Vbottom ones of answering relay 25, repeating coil winding 27 and grounded battery l5, completing the circuit to ground. The current thus allowed to iiow through the right hand. winding oi answering supervisory relay 21 is sufficient to maintain its arn'lature switch disengaged from its normal contact when current ceases to flow through the le'lt hand winding.

At the same time primary 7 at sub-station l receives operating current from grounded battery l and receiver 2 is placed in inductive relation with windings 26 and 27 of the repeating coil, Therefore, the party at substation l is telephonically connected with the operator who has responded to the line signal, as the actuation ot operators relay 22 connected operators telephone receiver 23 to the line ot the calling sub-station. A circuit fo;1 this connection may be traced as follows: from repeatingcoil winding 26 through the contact and engaged uppermost armature switch ot the two top ones of cperators relay 22, secondary of operators induction coil 3l, receiver 23, condenser 32, bottom armature switch and engaged left hand contact oit operators relay 22 and repeating coil. wii'idinp.` 2T.

lV hen cut-off relay 13 is actuated, simultaneously with the actuation of answering supervisory relay 2l. and operators relay 22. the audible signal in receiver 2 at substation l ceased. as limbs 9 and l() were disconnected from the variable current flowing through resistance 16. The cessation of this audible signal may be used as a notification to the party at sub-station l that an exchange operator is connected to his line and is ready to receive the number he wishes to be connected to, as answering relay is actuated as soon as answering supervisory relay 2l is actuated, thereby completing lthe telephonie connection between the calling party and the answering operator. Therefore. the usual verbal inquiry owt the t owever, the operator may converse with the `calling party, if desired or if necessary, by

means of operatorstransmitter 33 and primary 34 of the operators induction coil.

Having been told the number the calling party desires to be connected with, the operator tests the called for line by touching the sleeve `of one of the multiple jacks 36, associated with said line, with the tip contact o calling plug 35 in a manner well known in the art.

(The busy tests will be described herein-v after.) i

It the line tests not busy. calling plug is inserted in multiple jack 36, establishing a circuit which may be traced follows: from the grounded terminal ot.' cutolln relay 37, through the winding of the same, sleeve of multiple jack 36, sleeve contact. ot' calling plug 35. spring switch. 38 and engaged contact of calling relay 39, winding oil,t ringing relay 40, rightand left hand contacts connected by the bottom armature switch of actuated operators relay 22 and winding` 2T of the repeating coil, completing the circuit through grounded battery l5. The current flowing through this circuit clauses cut-off relay 37 to actuate removing line relay ll 'from the control of the substations connected therewith; Ringing relay 40 is alsoenergized by said current and its various armature switches are attracted. rlhe engagement of the top armature switch of said relay with its two contacts closes two circuits lirst and `then operates spring switches 42, 43 and 44 afterwards. The two bottom arma-ture switches of said relay are not attracted until after said engagement ot the top armature switch has taken place. Said circuits may he traced as tolloifs: first, 'from the upper terminal ol the winding of said relay through said armature switch and the left hand engaged contact, upper winding. of controlling relay 23.` spring switch. 42, (which is disengaged from its normal contact) spring switch 43, (which, in turn is disengaged from its normal contact) middle one of the three bottom armature switches and engaged contact ot answering relay 25. ringing interrupter L15, and grounded battery l5 completing the lcircuit through the circuit already traced through the winding of cut-olli relay 37. rlhe second circuit may be traced from the grounded terminal of magnetic clutch a6 ot party line ringing key 4.7, release hey 43, the winding of said clutch. supervisory lamp 4:9, right hand contact and engagedtop armature switeh et ringing relay Lt0, and the lett hand engaged contact of the same, coinpleting the circuit to ground through the circuit already traced through the upper winding of controlling relay 23 and ing interrupter d5. rlhe current thus lowed to tlow through said windingeneryvisory relay 21.

gif/:es relay 2?; and its armature switch diseng es 'its contact, opening the circuit through. thenfinding ot operator-s relay 22 and lett hand Winding ot' answering supen The consequent de-energization ot operators relay 22, releases its various r niature switches, removing' the operatorie nection' with the calling' sub-station and opening the energizing circuit ol ringing relay iit), Which has been traced 'from the upper terminal of the Winding oiE said relay through the tivo contacts ot the bottom armature switch of operatoi"s relay However, current still 'denis through the Winding of ringing relay llt), to maintain the same actuated, by vay ot the circuit traced through the upper Winding of controlling relay 23.

Yinswering supervisory relay 2l remains actuated, due to the described circuit through its right hand winding. Cutoff relay 1.3, also remains .actuated, due to the also described ycircuit through the Winding ot answering relay 25.

The insertion ot calling plug int-o multiple `jack 36, also closed another circuit which may be traced as follows: through the described circuit troni the grounded terminal of cut-oil relay 37 to the lower Winding` olf controlling relay 23, completing the circuitl through grounded battery 15. rFhis lower winding constitutes a locking Winding and is of a. preferably extremely hi gli resistance and is such that the current passing through the same. While not sutiicient to cause the disengagement oi the arma-ture switch ot' saiffi. relay from its` contact, sutiicient to maint-ain the same disengaged atter said disengagement has been accomplished by the current `flowing.through the upper winding ot' said relay.

The operation ort the tivo bottom armature suitches ot` ringing relay 40, impresses ringing current on the line oit the called for substation iu the manner fully described in my afores id patent, wherein is also described the means whereby callingl supervisory relay 50 and calling relay are actuated when the called t'or sub-station responds to its calling signal.

rlhe application ot the aforesaid ringing system to vpart).v line ringing will now be described.

The aforesaid connection with multiple jack 3G, as described, related to a line with a. single sub-station associated therewith. It the calling party had called for a sub-station on a party liner, previous to inserting calling plug 35 in multiple jack 36, the operator would have depressed the corresponding` party line key. ln the party line ringing system illustrated in Figure l. six ringing kcys are illustrated diagrammatically, numberedrespectivelyf from 5.1 to 5.6, both in- 'elcphone set vtrom telephonie cony clusive. Numbers 5l, 52, 55 `and 56 being single break l bers 53 and being double break and make 7 keys, so arranged that `their actuation also operates eitherkey number 51 or 52, as the case may be.

The hereinbe'liore described actuation of answering relay 25, (previous to the actua` tion ol ringing rela-y 40) closed ai circuit which may be traced as lolloivs 1' from the live pole oit grounded battery l5, through ringing interrupter 45, cont-act and engaged middle armature switch of the three bottom ones of answering relay 25, spring switch Li3 and normal contact ot ringing relay l0, supervisory lampV 57, Winding of magnetic clutchA 46, release key 48 complet ing the circuit to ground. Such magnetic clutches are Well known in this art and need not be herein described in detail. The current flowing through the Winding oi said clutch is sutiicient to maintain the switch springs ot the party line ringing keys engaged with their alternate contacts, after the same have been so engaged manually. It the party called for is represented by one ring ot positive pulsating current on the limb of the line connected vtothe tip springr of multiple jack 36,'then the operator would depress key 5l betere inserting calling plug 35 into multiple jack 36. The current tloW- ing through the Winding ot magnetic clutch 4:6, is not interrupted by the described actuation olf ringing .relay et), though atter said actuation the operating current for the inagnetic clutch tioivs through supervisory lamp i9 instead ot supervisory lamp 57. This result is obtained by means ot a circuit which may be traced as follows: from the live pole ot grounded battery l5, through Waiting inn terrupter 58, contact and engaged lowerniost armature switch ot the two top ones of answering relay 25, normal contact and spring switch Ll2 ot ringing relay 40, upper Winding oit controlling rel ay Q3, the two contacts of the top armature switch ot ringing relay 40, which are connected together by the operation oit said armature switch, supervisory lamp i9 and Winding ot magnetic clutch 4G, con'ipleting the circuit to ground through release key fl. iis hereinbefore described the top armature switch ot' ringing relay 40, engages its tivo contacts before the operation of spring switcl 's 42. and 43, therefore the last described circuit through supervisory lamp 49 is made previous to the opening` ot the circuit through supervisory lamp 57. As spring switch 43 'engages spring switch 42' betere the latter becomes disengaged from its normal contact, connecting said spring switch to Waiting interrupter 58, the current flowing; through supervisory lamp elf) also is not interrupted, notwithstandingl the completed actuation ot ringing relay l0 substitutes current from ringing7 and make keys and num-y ifi-aisee interrupter .15 for current from waiting interrupter 58. f

Having depressed party line ringing key 51 and inserted calling plug 155 into multiple jack 3b a circuit for the 'proper ringing current may be traced as follows: from the grounded brush of 'alternatingcurrent ringing generator 59, through the latter, interruptor 60, brush 6.1, interrupter and its brush. alternate contact and engaged spring switch of liey 5l. alternate contact and engaged uppermost armature switch of 'the two bottom `ones of ringing relay at). non-inductive resistance (i3, normal contact and left spring swim-h of key 54%. normal Contact and right spring switch of key :3f-l. tip Contact of calling plug 35, tip

spring of multiple jaclf; S6. limb Gil of the` called sub-station line.l condensers and biased bells at the sub-stations associated with said limb, limb G5, ring spring of multiple jack` 3G, ring contact of calling plug. 35, `left spring switch and engaged normal contact of key 53, right springv sivitclnand engaged normal Contact of key oel. winding 29 of the repeating coil, spring switch ai and engaged contact of ringing relay Ll0, spring switch and normal contact of lzey 553 and `spring only in contact with brush 6i during a period which represents tri'iie less than onequarter of the revolution of said interrupter. Then the center of the exposed metallic portion of said interrupter is engaged with brush 6].. the voltage of the positive current produced b-y alternating current generator 59 and delivered to said interruptor is at its maximum, the insulated portion of saidinterruptor being` engaged with said brush during the period when the volt i of the positive current delivered to said interruptor is increasing or (lecreasing and the current changing from positive to negatif-fe. nother circuit may be traced through alternating current generator 59, as follows: from the grounded brush of said generator, through the `latter and primary of transformer 69 completingthe circuit to ground. Said transformer is of the set-down type, so

that the voltage produced in the secondary thereof is so low that the current flowing through saidsecondary will not operate the call bells or annunciators of the lines which may be connected `to said secondary, even `though said bells may he biased to the polarity taken off from said secondary. circuit may be traced 'from ground. through said and it has secondary, interrupter il), brush Tl, and thence over the same route followed by the current delivered by interrupter 60. linterrupter 70 is a counterpart of interrupter 60, only the center of its exposed metallic portion engages brush 7l when the voltage of the negative current produced in the secondary of transformer G9 and delivered to said interrupter is at its maximum. Both interrupters and 7() are so mounted that they revolve in synchronism with the armature of ringing generator 59, being preferably mounted on the same shaft. Therefore the vcurrent delivered to interruptor 62 is an alterna-ting one, though the voltage ofthe positive alternation is that of generator 'while the voltage of 'the negative alter nation is that of the secondary of step down transformer` 69. instead of transformer 69 it will he seen that another generator producing a voltage lower than that of generator 59 might be used, the connection to interruptor 7() being the same as that from generator 59 to interrupter (Si). As the use of the. transformer entails the use of but one generator, l have so illustrated the system in the drawing'.

A circuit las been traced from inte'rrupter 62 through limb 64k and the biased call bells or annunciators associated with said limb, been mentioned that call bellsor annunciators 6G, 67, and 68 alone are operated. rlhis action is due to the factthat While negativecurrent is delivered to limbf. from transformer 69 through interrupter 62, its voltage is so low that biased bells 72,

733 and 74 (which are adjusted 'to be operated only by the delivery of negative current to said limb 64 of the voltage of alternating current ringing lGenerator 59)` are not operated thereby. llowever, the voltage of said negative current is suiiicient to cause the condensers in `series with call bells or animnciators 66, G7 and (3S to allow the passage of the high voltage positive current, thereby causing the operation of said bells or annunciators. This claim vis novel means of operating biased bells or annun ciators or of selectively ringing plurality of call bells or annunciators when bridged in series withcondensers across a party telephone line, for While the ringing current used is an alternating one in fact, in operation itis virtually a pulsating current.

Interruptor 62 revolves slowly so that the signals produced at the respective sub-stations are intermittent ones, the length of the ringing and silent intervals being purely arbitrary and can be adjusted according 'to the respective size ofthe metallic and insulatme GCI eating vvhich' one o'l' the three sub-'stations was desired. li' the calling party desired the sub-station responding to tivo rings the operator-Would have depressed key 56, as Well as key 5l. ln 'which event the circuit for he ringingl current which Was traced to ground through lie 7s 55 and 5G and their normal contacts would have been traced through the spi switch ot key 55 and its alternate contact and inten rupter 75 to ground. lnterrupters ('32, T5, 7G, 77 and 78 are prei rably o'f the same size and so mounted that they all revolve at the same speed, andthe insulatiun` segments ot interrupter 75 engage its brush vlien the respective brushes ot interrupters 62, 77 and 7S are in engagement ivith the renter ot. their respective metallic segments. ln this Way the ringing period is broken up into tivo peg riods by means oi the insulating segments of interrrupter '75. lit three rings had been called for, then key would have been depressed, instead of key 5G, and the ringing period would have been broken up into three periods. lt will he seen that tour rings or` any other desired number could be obtained in the same marmer.A also that thel ringing signals produced by .interrupters T5 and 76 could be made to consist oi? short and long,` rings by merely arranging,v the insulat ing' segments ot said interrupters accorciinsly.

`Had the call been for either sub-station 72, 73 ror 74, which require high voltage negative vcurrent connected to limb 64, then the operator would have depressed key 52 instead of key 5l, at the saine ne depressing key 55 or 56 il the call was tor tivo or three rings. The current delivered to limb 64. in that event, would have been thatrfrom kinterrupter 77, which is connected to brushes T9 and 80 oiC interrupters GO and '70. Das said interrupters are arranged to revolve at the same speed as the armature oit alternating current ringing` generator a9, brush 79 engaging the center ot the metallic portionI oli interrupter 60, when the negative curreiit delivered to said interrupter is at its mum` and brush 80 engaging the center ot the metallic portion oip4 interrupter T0 when thewpositive current delivered to said interrupter by the ksecondary of step down transformer' 69 it at its maximum, the ringing current impressed on limb G-Li by the depression ot key 52, is the reverse of that iinpressed thereon. by the depression of key 51, and theretore call bells or annunciators 72, 73 and 74 'Will be operated. Call bells or annunciators 66, G7 and 68 are not operated by the low voltage positive current s iinpressed upon said limb, as they are so adiusted as to require tor their operation positive current of the potential ot ringing;i generator 59.

ifisisee Had the callbeen 'for either sub-station 82 or 83, which require high voltage positive current to be delivered to limb 65, then the operator would have depressed key 53, instead ot either key i or 52; at the saine tinie depressing key 55 'or 55 if the call was for tivo or three rings. By depressing key 53, the connections tothe tip and ring contacts oi calling plus; are reversed and at the saine time actuating member Si, insulated from the springs, depresses key 5l. By this mean-e; the ringing circuit traced through interruptor G2 is reversed and the current from said interrupter is impressed on limb 65 instead of limb 64.

lilad the call been for either sub-station 85, 86 or 87, which require high voltage negative current to be delivered to limb, G5, then the operator would have depressed key 54,

instead of either key 5l, 52 o1 `53; at the Same time depressing key or 56 it' the call was for tivo or three rings. By depressing key 54, the connections to the tip and rinii; contacts ot calling plug 35 are also reversed, and at the same time actuating member 88, insulated from the springs, deprcsses key 52. By this means the ringing circuit traced through interruptei' 77 is reversed and the current from said interrupter is impressed on limb 65.

It will be noted that the code ringing is produced by rkeys Which are not individual 'to each type or' ringing current used but instead are common to both types, refifardless of the limb of the telephone linebthey inay bev connected to. )l claim this as a distinct advantage over the usual type ot automatic code ringing which requires code keys individual to the type of current used, as less keys are needed resulting' in less expense, maintenance andv occupied space on the key shelf ot' the switchboard. Also keys 55 and 0.6 can be'use'd to turnish code ringing tor lines requiring the regular alternatingr ringingl current. I

lt shoilild be understood that the described ipeaiiJ pl'iereby an alternating' 'current is producer tiring a high potential alternation o't onepolarity and a lou' potential alternationLoi another polarity could be 'used without the association with battery interrupter 9i in which event the exposed inetalliclportions ot interrupters 6l and 7l might be enlarged and the current taken oli from the saine during' a complete alternation instead of about one halt an alternation as hereinbeiore described.

Had the call ybeen for al one party line, then the operator would have inserted callinfrA lue 35 into multi le 'ack 36 Without n ya depressing,` any ringing key. I 012mm hlS 1S a distinct advantage over those ringing systems which require a key to be depressed or manipulated Ytor every connection made to a called for line, as the operators time is saved thereby7 the majority ot connections made through a switchboard being usually to non-party lines. y

lVhen suchA a connection .is made, the ringing circuit may be traced 'from ground through ringing generator 5S), interrupters 8S) and 78 normal contact and spring switch of key 52, normal contact and spring switch of key 51, whence the circuit proceeds over the course already traced. Interruptor S9 is dill'erent :troni interrupters 60 and 70, though it revolves at the same speed as they do, inasmuch' as the exposed metallic portion is adapted to engage its brush when both the positive and negative current delivered to said interrupter Pfrom ringing generator 59 is at its maximum. rilhere'liore both the positive and negative current impressed upon the called for line is oit the potential of ringing generator 59, and the call bell or annunciator 5 in series with condenser G of a nonparty line shown at sub-station 1) is operated thereby.

The i return ot the ringing current to ground, whichever ringing key or keys are depressed or manipulated7 is always through winding 29 of the repeating coil and as telephone receiver 2, at sub-station 1, is in inductive relation to windings 26 and 27 ot said repeating coil the ringing signals are heard in said receiver by the party at said sub-station, thereby assuring him that the called for sub-station is being rung.

It code ringing is used the depression of the wrong code key would therefore be indicated to the calling l,party who would thereupon rectify the error.

The energization of controlling relay 23 and the consequent disengagement of its armature switch with its contact has been shown to take place when ringing relay 40 is actuated` due to the insertion of calling plug into multiple jack 36. By making this relay oi a slow-acting type, by any oi" the niechanicah electrical or magnetic means well known in the art, operators receiver 8 would remain bridged across repeating coil windings 26 and 27 until atter thelirst ringing signal had been given. By this means the operator would hear said ringing signal in the sameway as the party at sub-station l., the absence of said signal being an indication of an open line or faulty connection in the ringing` circuit, and it code ringing is used would .serve as a check on the correct key having been depressed or manipulated.

When the party at a called sub-station` responds to the calling signal (regardless of whether it is a partvline or not limbs and G5 are connected together through the sub-station telephone apparatus, as described in relation to sub-station 1. (Said apparatus is not shown in association with the sub-station call bells lfor sake of clearness.) The call bell or annunciator 5 and condenser 6 up to this point allowed `the passage ot' alternating current only through limbs and X but now the passage of direct current is allowed as well and a new circuit is closed 'which may be traced as follows: trom ground at key 5G or interruptor 75 or 76, as the case may be7 according to whether the ring has been a code or not, through said key or interrupter, engaged contact and spring switch ist of ringing relay 40, winding 29 ot the repeating coil, lreys and to either the tip or ring contact of calling plug 35, as the case may be, according to "whether party line ringing keys 555 or 5st hare been depressed or not, one of the si'irings ot multiple ach 36, one of the limbs of the line called lor, primary T, switch-hook et, transmitter 3 (as shown at sub-station l), the other limb of the line, other spring ot multiple jack 35, either tip or ring Contact of calling plug 357 keys 53 and 5l, winding of calling supervisory relay 507 spring switchfil) and engaged armature switch oit ringing relay Ll0 and interrupter 91, completing); the circuit through grounded battery 15.

lnterrupter 91 is a counterpart o'l interi'upter 89 and revolves at the saine speed, which is lthat of the armature ol ringing generator 59, but is so mounted that its brushengages its exposed metallic portion only when the brusiies oit interrupters (50, and 89 are in engagement with their insulating portions. t will therefore be seen that ringing current trominterrupters G0, 70 and 89 can never pass through non-inductive resistance ('33, winding ol calling super-V visory relay 50,` spring switch 9() and engaged armature switch o'l ringingv relay 4() and interrupter 91 to ground through grounded battery 15, nor can direct current from said interrupter 91 everipass through said interrupters (SO, T0 and 89, but that alternating with each valternation ot the ringing current from ringijing generator 59` direct current will be sent through said winding of calling supervisory lrelay 5U and alternating current through said non-inducn tire resistance G3, the circuits in both cases being completed through the limbs of the called for line only.

The rapid intermittent direct current sent through the winding otcalling supervisory relay '50, by way `ot interruptor 91j `when the described circuit for direct current is `closed at the called "r'or sub-station. is smilicient to cause the energization of said relay and the consequentv engagement of its arma ture switch with Aits alternate contact, which closes a circuit which may be traced as tol low i Atroni the grounded terminal oif ciitoit relay $37, through the winding ot the saine. sleeve oi multiple jack 3G, sleeve contact oi calling plug` 235 alternate contact and engaged armature switch ot calling super `lll) visory relay 50, winding ot calling relay 39 and talking interrupter 24, completing the circuit to ground through.grounded battery 15. T he current thus allowed to tlow through the winding olf calling relay 39 energizes the saine, its uppermost one ot the two top armature switches and its bottom one lirst engage their respective contacts and lthen spring switch 38, disengages its normal contact. rlhis disengagement opens the circuit through the winding oi ri fing relay elO, which thereupon releases itsV various armature switches which resume their normal positions. The disengagement ol. the uppermost one of the two bottom armature switches of said relay 'from its alternate contact opens the circuit to the ringing interrupters by way of party line ringing keys l and and connects non-inductive resistance ('33 to the normal Contact ot spring switch 90 by the engagement of said armature switch with its normal contact. The

, lowermost one ot the two bottom armature ter 91.

visory relay 50.2' As a ground connection 'from the upper terminaliof winding 29 oit the repeating coil was made by the engagement with its contact of the uppermost one ol the two top armature switches ot calling relay 39, previous to the disengagement ot spring switch 4i-4 ot' ringing relay Ll0 from its contact, the current passing through the winding ot calling supervisory relay 50 is notI interrupted. notwithstanding the 'tact that its connections have been. changed.

When springswitch 38 of calling relay 99 disengaged its normal contact its engagement withits alternate contact formed a shunt circuit around the armature switch and engaged alternate contact of calling supervisory relay 50. By means of this shunt circuit a possible intermittent current through the winding `oli calling relay 39, due to a possible intermittent engagement of said armature switch with said alternate contact, due in turn, to the intermittent current flowing through interrupter 91, is thereby avoided. It preferred, the contacts closed by the actuation of calling relay 39 are made as illustrated in Figures 17 and 19 in relation to the corresponding calling relays therein. ln these forms the contacts are made in sequence and ringing relay ll() Therefore current is not cle-energized until after said shunt circuit has been first established.

rlhe engagement oit the lowerm'ost of the two top armature switches ot calling relay E9 with its contact, causes the energization.

oit called line talking supervisory lamp 93.

The disengagement of the top armature switch ot ringing relay 4l() from its two con` tacts, extinguishes ringing supervisory lanjip li9 and opens the circuit through the upper winding of controlling relay However, as has been already mentioned,

`the current flowing through the lower winding of said relay maintainsiits armature switch disengaged from its contact. The

engagement oi"I spring switch l-l, oi ringing can be made without removing the linlr connector used to establish the previous connection. Also, whenever a telephone receiver is replaced upon its switch-hook at either of the connected sub-stations. that line will at once test not busy at all thc multiplo jacks associated with said line. In other words the taking down of `the connection made by means of one'ot the link connectors is not essential to the clearing ot' the lines` Vlor A.Furi ier connections thereto.

lli/*hen answering relay Q5 actuated. as hereinbet'ore described, a circuit was closed which has not been heretofore traced or dcscribed. This circuit may be traced as Ltollows: Vl'roin the live pole ot grounded battery 5 through talking interrupter 2l, uppermost one oit the three bottom armature switches and engaged contact ot answering relay 25, to the center terminal ot the winding of said relay, through the upper portion of said winding, sleeve contact ot answering plug 20, sleeve contact ot answering jack 12 and winding of cut-olf relay 13, coinpleting the circuit through grounded battery 1.5. This circuit short-circuits the lower halt` of the winding of answering relay 25, which received current from interriipter 24, in the first place, through the alternate contact and armatureswitch ot.' answering supervisoryrelay v21. Then the calling part-y at sub-station 1 vreplaces receiver i?. upon switch-hook 1, the circuit through the right hand winding of answering supervisory relay 2l is opened and the Les;

armature switch ol: said relay diseneages its alternate contact and engages its normal contact which is connected to the sleeve oontact oit answering plupv 20. rllhe current from nterrupter 241 now has two paths leadingl from the central terminal ot the winding ol answering relay 25, one towards the upper terminal of said winding and thence to said sleeve contact and one towards the bottoni terminal ot said windinga and thence through. said armature switch and normal contact of answering;` supervisory relay 2l to said sleeve. As these two windings are opposed to each other, relay becomes deenergized and its various armature switches disenirage ,their respective cont y s1 (one ot the objects in arranging); tor such a lle-enereization of answering` relay is on account of the sensitive action inherent in supervisory relays which are inserted in the talliinglj circuits. A momentary clisengao,A nent ofthe armature switch. ot answeringY supervisory relay `2l from its alternate contact will not release answering relay 9,5, due to .the shunt circuit around said arinature switch, it being; necessary tor said armature `switch to fall all the way baclt and ene'aee its normal contact before said release can he effected.) Current thereby `out orT 'from the tip, ringl and sleeve contacts ot answeringr plug` 2O and therefore cut-oil relay lll is de-energized, its arn'iature switches engaging' their contacts thereby restoring lino relay let and line lamp or signal 17 to the control ofthe apparatus at sub-station l. It will be seen. therefore, that it is inima- ,terial whether answering` plugl Q0 is removed or not from answeringV jack 12, as the three strands ot the linlr connector are all open and from an operating;l standpoint there is no connection trein the jack to the linl; connector. As loney as calling` plus; remains connected `to the multiple jack ofthe vallei line, controlling relay 22% ren'iai'ns actuated thereby maintainin;- the circiiit open trom cut-oil relay'lfl1 'hroueh the lett hand winding ot answering; supervisory relay Q1. and operators relay 22.

When the party at the called sub-station reifilaces receiver upon switch-hook 4l the circuit through the winding' oi callinp; supervisory relay 50 is vopened and. its armature switch discnragres its alternate contact and engages its normal contactR thereby shortcirc-uitingr the winding; oit callin@ relay 39. lfheA path lor this short-circuit may be traced liroin the upper terminal oit the windinf; calling' relay 391 through fl arinatureswitch and normal Contact. oVx collhe' siipeii'isory relay 50, to the lower terminal ol winding' ot said calline relayslf). Due to this short-circuit (the object which is the saine as described in reference to answering? supervisory r y 2l) y 39 'is deenergeetl and its Various armat switches dsub-station waiting the recalli,

and sprl switches resume their normal positions. most, one of the two top armature switches ci!" said' relay opens the path to ground from winding` 29 of the repeat-ing coil, and the disengagement ot the bottom one from itsA contact opens the circuit through winding 30 of the repeatine` coil. Therefore, the tip and ri'ne` contacts of callingv plug are disconnected troni any source ol "current and raniiot be again connected theretoj untilcallfingr plug` has first been removed from nniltiple jack However, the circuit hereinljmiforetraced. through cut-oil relay' and the lower winding' of controlling relay 23, is still maintained, flhere'tore said controlling relay continues to maintain its armature switch disengaged trom its" Contact. yAs the lower winding ol: controlling relay is of an e t remely high resistance,"the current allowed. to pass through it is not sullicient to maint-ain cut-oit relay 3? in an actuated condition and as the circuits through both ringrelay 40 and calling' relay 89 have now n opened, `the armature switches of cutl relay engage their normal contacts7 thereby r storing-r line relay lll to the control oli tationsassociatedwith Therene* an established connection by a l -stations desires another connection, it is only necessary to depress, momentarily u `tch-hook l and the `link connector is' inntly diseminected lrom the line and the cori-espendinglinelamp `or l? is displayed. .ln the case of the called-.substation this display might occur, at an operators iliosition other than the oneatl which the tiret connection was established]- In the case oji the calling sub-station the recall would occur at the saine position `where Vthebiirst conne on was established and itwould lonly be. nec y the oijier'ator thereat to remore calunw` plug; flo yfrom multiple'jaehv 36 in order to at once placey operators receiver in talking; relation again with .the callingr This is bre o'ht about bythe de-energi/ati'on of controlling; relay which occurs as soon as the connection be ,weon the sleeyecontactyof mul,- tiple jack :EQ and the sleeve Contact ot call- 'ii plug 35 isbrolten. i

lines which testell not busy. When .the

.tip ot' calling pluri was applied to ythe 'trom ground through primary 94 ol. opera-` tors induction coil. s primary bein@r refl L i b A erably et' a high resistance,contacten@155111 The disengagement ol theuppe'r-` 'alec-tor9 it one or both ot the connecteine current was being' impressed y roo .llhe described connections Lwere made .to

fai)

gaged lowermost armature switch of the two top ones of opera-tors relay 22, tip contact of calling plug 35, sleeve of multiple jack 36 of the tested line, sleeve of the multiple jack associated with said line to which is connected the link connector impressing ringing current on said line, sleeve Contact of calling plug 85 of said link connector, and thence to ringing interrupter 45 by way of the circuit which has already been traced, completing the circuit to ground through grounded battery l5. As ringing interrupter 45 similar in character to the described interrupter 18, though its insulating segments are different, a direct cur rentis furnished thereby which is not of asmooth quality or while continuous is `pulsating in character. Therefore the Icurrent flowing through the described circuit fluctuates or varies and therefore primary 94 of operators induction coil induces an alternating current in secondary 32, which is heard as an audible signal in operators receiver 28. This signal would be distinctive in `character to ringing interrupter 45. As said secondary 32 and said vreceiver 28 are bridged across windings 26 and 27 of the repeating coil, this audible signal is also heard by the party at sub-station l., so that the report of the operatorv that the line is being rung upon is confirmed. In fact, such verbal report of the operator may be done away with altogether and the audible signal alone can serve as the notification to the party at sub-station l.

When the described busy test was made on the busy line, had the party at the called sub-station already responded to the calling signal `and had removed the receiver from its switch-hook, then calling relay 39 of the already connected link connector would have been actuated and ringing relay 40 cie-energized, and the busy test circ-uit from the sleeve contact of calling plug` 35 of said link connector would have been through the winding of calling relay 39 to ground through talking interrupter 24 and grounded battery l5, As this interrupter is adapted to furnish a direc-t current which fluctuates or varies in a distinct manner from that of ringing interruptor 45, the audible signals produced in receiver 28 and sub-station receiver 2 are also of a distinct character and the operator and the calling party would know that the called for line was being talked upon or held for conversation If t-he tested busy line had been one which initiated the call, then the circuit from thethirnble of the tester multiple jack would have been to the thirnble of the answering jack associated with the same line and thence through the winding of answering relay 25 to ground through the sameinterrupter 24. y

When the described busy test iS made on an idle line, if there is no calling plug connected to a multiple jack associated with said line, then the sleeve of the tested j ack would be at the potential of the earth and primary 94 of operators induction coil would not be energized and consequent-ly no audible signal produced in operators receiver 28. If a calling plug was so connected to said tested line, but both ringing I relay 40 and calling relay 39 had been deenergized, as has been hereinbefore described, then the sleeve of the' tested jack would be at a potential above that of the earth.y due to the current Flowing from the live pole of grounded battery l5, through the lower, locking winding of controlling relay 23, which current Hows through the sleeve contact of calling plug 35 and the thimble of the engaged multiple jack. However, due to the extremely high resistance of said locking` winding, the current which could flow to ground through primary 94 of operators induction coil, when a busy test is so made is extremely small and the audible signal, if produced at all, in operators receiver 28, would be heard as an extremely faint click. As all the busy signals consist of loud stained tones`r due to interrupters 24, and 58, an operator has no ditculty in understanding that said possible faint click does not indicate a busy line.

In both described cases of a busy line, the calling party can request awaiting connection if desired, and upon receiving this request the operator would at once insert calling plug into multiple jack 86 and pay no more attention to the connection until the de-energization of all the supervisory lamps indicated the-established connection could be taken down. When calling` plug is inserted in a spring jack associated -with al busy line the V'circuit through the tip andring strands of the link connector attached to said plug are not closed until the line has been released from the connection previously made to it. Said release. as has been fully described, taking place when the receiver at the busy substation is replaced upon its switclrhook.

As long` as the circuit through the tip and ring str 5 attached to the calling plug is open` it will be seen that no interference can be made with the conversation going on between the tested luisv line and the line to which it is connected. neither cau the waiting party, overlieai' anyv of the conversation passing between saidlines.

The use of such interrupters as 24, 45 and 58 for the busy tests is disclosed in my before mentioned il. S. Patent No. 1,128,262, therefore no further description is considered necessary.

The prevention of interference with the talking circuit at a busy line when a .sub-station is connected to the `,5y-,ns e* `spring switches waiting rconnection `is made` is brought about partly by the comparatively high re-` sistancerot eut-oil relays 13 and 3T and partly by the two-part windings of .answerf ing relay 25 and ringing` relayed). lllhen calling plug 35 is insertedin a multiple jack associated with an idle line anda calling plug of the same link connector, all vvthe cur rent which can pass `through the winding of cut-,off relay 37 flows through the complete winding of ringing relay 40. `This current` is suliicient to actuate ringing relay l0 and y the `engagement ofthe top armature switch of said relay with its lefthand contact, forcesl the spring switch associatedywithsaid ,Contact into engagement with contact 95 which is connected to the center oit said winding` ot ringing relay 40, thereby short `circuiting the upper portion of said winding. Il an other connection is thereattermade to an other multiple jack associated with. the saine line, the current ,flowing thigough the high resistance winding of cut-off relaji 37, has two paths `o'ered it.y one 'through `the klow resist-ance of ringingrelay 40 which has had the upper part of its windingshortcircuited and the other path through the high resistance of the complete windingot ringing relay 40 associated with the link connector used for establishing ,the waiting'i' connection. Ringing` lrelay l0 is `such that not enough current from `cut-ofi relay 3T can flow through its complete windingl to operate its various armature switches and when said winding isy shunted by the low resistance path of `another ringing relay 40 which has had the upper part o't' its winding shoi't-Ycircuited, as described. However, enough current doe; pass through said complete winding tocause the top armature switch of said ringing relay l0 to engageits two contacts. y i

As'spring switch 4&3, oi? ringing; relay l() does not disengage its normal Contact. supervisory lamp ,57 remains energizedjand as spring switch l2 does not ,disengage its normal Contact, the current which flows through the upper winding of controlling relay and 3the complete winding ot ringingV relay l0 .emanates from waiting77 interrupter- `5S, instead ot ringing interrupter asr-:ould have been the case had ringing relay t() fully actuated. As waiting interrupter .58 tun nishes a fluctiuitinnor variable current ol different character to either ringing in-.

ing .ringing relay Die its "Wat i ing .conditionL therefore the operators telephone set is disconnected from the link connector as. hereinbeitore described. VAlso `said relay remains actuated by means ot the current'ilowinp; through its lower winding,

notwithstanding the fact that another link rent and therefore the remainder of its armature `switches and spring` switches do not i operate. However. when the receiver or' the. called sub-stationr is replaced 'upon its switch-hook, then the circuitftor the current from the winding of cut-ofi' relay 8f? to calling relay 39 is opened and the full 'force ot `the current allowed to passy through `the winding of said cut-off` relay 337 now passes y through the complete winding of ringing relay Ll() associated with the link connector in the waiting condition. rl`he remaining armature switches andspring switches of.

`said relay thereupon engage or disengage their respective contacts. `with contact 95 oil-the spring switch asso- Tlie engagement ciatedwith the left hand contact of the top armature switch, in turn, short-circuits ythe `upper portion of the windingfof said ringing relay, sokthat `any 'further connections made to the same line will be placed vin the waiting condition.k The described .delayed action ofjringing relay --O impresses ringing .current on the formerly busy line in the same manner as has been fully described. ,lf the call had been .tor a dilerent sub-station Lthan the one in use on the kbusy line` the correct ringing current would `be transmitted `as cp- 1 erating current for magnetic `clutch el@ would have been `furnished through supersoy `visory lamps 49 and 57aiid vrthe correct rin eine; i

key or keys would have been depressed before or attei' the waiting connection was made.

`When the described waiting ,connec- `tion was made. if calling relay'SQ ol ther the saine results would be brought about in regard tothe waiting link connector, due to the Atact7 as hereinbefore mentioned. that the rresistance of said relay fis that ot the lower part oi" the winding oi: ringing` relay `LA), ,therefore ringing` relay el() ofthe waiting link connectorlis stillshuntcd by a low` resistance path. i y y lVhen the described waiting` connection `was made.I .it the `tested line had been one that had initiated .the call then the circuit teem the .Outfeff 'teler fWOillSl have been through answering relay Q5, instead of ringing relay l() or calling `relay 39. Answering relay `has a winding"exactly` similar to that of ringing relaylll), one-half of its winding having-been short-circuitedi'by the engagement ofthe uppermost one of the three bottoni armature iitches with itscontact, as has been described. Therefore, the same .results are accomplished when a waiting connection is made to the line associated with said answering relay.

It will be seen that the described waiting connection lwould be brought about, should an operator carelessly connect a calling sub-station to a busy line, withouthaving been requested so todo. rJ'herefore I furnish means whereby it is impossible to telephonically connect rthree lines together andtherefore I evade the confusion which i is energized by the current'flowing therethrough, and another circuit has been traced through the armature switch and engaged alternate contact of said relay, said circuit including the complete winding of answering relay 25. Therefore if the'current allowed to pass through theV high resistance winding of cut-od relay 13 has an alternative path through the low resistance of anvother'answering relay 25 which has had the Alowerpart of its winding short circuited by its actuation, as has been describedJ this low resistance shunt 'is sufficient to prevent 'enough current owing through the high resistance path offered by the complete winding of the first mentioned answering `relay 25, to actuate the same. As the tip and ring strand circuits connected to the answering plug remain open until answering relay 25 has actuated it will be seen that no interruption to a conversation can be brought about by the connect-ion to a busy line of an answering plug and that an operator 'cannot thereby connect her telephone set to said busy line.

From the description so far gireinit willbe seen that it is impossible for an operator to listen to aconversa-tion passingthrough a linlt connector, as controlling relay is actuated as soon as a. connection is made by'means of calling plug and therefore the circuit through operators relay 22 is opened, preventing thereby, the association of operators receiver 28 with said link connector.

iTherefore, the talking or listening capacity of an operator is strictly limited to answer Ving-calls initiated at calling sub-stations and neither said operator nor another party at a rsub-station can interfere in any way with -a duties of the operator give an opportunity or make it convenient to remove them, the

usual operation of the supervisory signals,

for the sake of economy in consumption of current, has been reversedand the supervisory lamps are energized while the substations are busy and are extinguished when the respective receivers are placed upon their switch-hooks. As the system hereinbefore described vincludes automatic ringing and automatic waiting, it also includes supervisory signals distinctive lto these operations as well as distinctive to the ctalking condition of the link connector. In order to simplify these signals, reduce the number of lamps used and to curtail the supervisory work. entailed Aon an voperator by the observation of a plurality of supervisory lamps, I use but three lamps'for this purpose and by the energization of one orl more ofthe same I am enabled to obtain five distinct signals. To still further reduce the supervisory work of the operator, the preferred way of mounting the three supervisory lamps is as shown diagrammatically in Figure l, where the three lamps are shown close together and 'mounted under one transparent or semi-transparent cap 96, so that in operation the effect is the same as if but one lamp was used. In other words, the operator has to observe what would correspond ordinarily to but one lamp. To obtain theiive mentioned supervisory signals the three lamps are of different colors7 and while I do not wish to be limitedto any particular color combination (as there are many such), I have' found the following very satisfactory, to wit: red for lamp 57, which is controlled by answering y'relay 25; yellow for lamp 49, which is vcontrolled by ringing relay 40; and blue for lamp 93, which is controlled by calling relay 89.

l.When answering plug 2() is inserted in' a jack and answeringl relay 25 has actuated, a red light is therefore shown through cap 96. This color, whenever displayed, indicates that the calling party is still connected t0 the link connector and that no other connection is made therewith.

When calling plug 35 .of-thesarne link connector is inserted in a jack oi a busy line, then lamp i9 (controlled by the top armature switch ot ringing relay 40) is also energized, lainp 57 remaining energized owing to the tact that spring switch i3 ot' ringing relay di) has not disengaged its normal contact. The elif'ect of the red and yellow lamps both being energized is to show an orange light through 'cap Sie. This color. whenever displayed, indicates that the calling party is waiting7 on a busy line.

lhen calling plug Si oi? the same link connector is inserted in the jack of an idle line, then lamp 57 is extinguished by means ot spring switch i8 of ringing relay e() disengaging its normal Contact, therefore lamp 49 alone remains energized and shows a yellow light through cap 96. This color, whenever displayed, indicates that the called for line is being rung upon.

W'hen the called for party responds and callingrelay 39 has actuated, lamp 93 is energized, lamp 49 is extinquished and lamp 57 is again energized by the ile-energization oi ringing relay 40. The eiiect ot the red and blue lamps both being energized is to show a purple light through cap 96. This color, whenever displayed, indicates that the calling' and called parties are conversing or are holding the connection for con-versational purposes.

7hen a calling party replaces the rcceiver upon its switch-hook and the called party does not do the same, then the conseuent extinguishing of lamp 57 causes a blue light to be shown under cap 96. This color, whenever displayed indicates that the called party is still connected to the link connector and that the calling party is disconnected thereto. As all three of the lamps are mounted in series with the winding of magnetic clutch 413 the resistance 0i the same diminishes lthe intensity of the lamps when two are burning so that the light produced by the two lamps is practically the same that produced by one. When party line ringing keys are not used a resistance may be substituted for said winding. Instead of mounting the lamps as shown and described, they can be all ot one color and mounted separately, in which event the signals would be according to those energized.

ln practice an operator would pay no attention to any one of the described supervisory signals unless one such was displayed for an inordinate time, when the matter would be investigated by said operator or another otlicial and any desired action taken. For instance, the continued display of the color yellow would indicate that the called Sii made toa line over which'a yvery long conf versation was being held, or that the receiver at thev desired sub-station had been left oid its switch-hook, and thecalling' party ator observes the supervisory signals, and

for the sake of convenience, takes down those link connectors which do not display any supervisory signal.

` However, should an operator be con-tronted by a shortage of link connectors the connections which displayed red or blue lights could be taken down and the link connectors used for establishing new connections. Also, il any link connector displayed an orange light it could be disconnected from the called line and connected to a special operator who would inform the waiting party that the called party had not yet released his line and that the "fwaiting party would be called as soon as the line was available. manner the release of the link `connector would be obtained.

The connection from the lower terminal of the lower winding ot controlling relay 23 and from the normal Contact of said relay, is shown as made to the live pole of grounded battery 15. lf preferred this con nection could be made to the corresponding pole ot another grounded battery and the action of both operatoi"s relay 22 and con` trolling relay 23 made more sensitive thereby, as the respective windings would not be shunted by other circuits. y

Many other changes and modiiications of the described circuits may be made without departing from the spirit and scope ot the invention.

It will be noted that the tip and ringy strand circuitsV of the calling link connector do not pass through all they various party line ringing keys in series, as is the case in other party line ringing systems in general use, but that said circuits only pass through reversing keys 53 and 54. This l claim `is a distinct advantage as much trouble is e.X-. `perienced with the old style ringing keys due to the increased resistance in the talking circuit due to the multiplicity ot contacts in the party line ringing keys which the talking circ-uit traversed. `Also it one oi said contacts should become loose the talking etliciency of the associate link connector isV impaired or destroyed. y

l have shown 1n Figure Q. how reversing keys 53 and 54 can be done away with, by

lll)

the case of a ring-ing"7 sired sub-station on a party line. By using such a` combination of cords, the party line ringing keys can he greatly simplified and the talking circuit of the link connectors would not traverse any key contacts.

yRelease key 48 ot' magnetic clutch 46 is provided so that in case an operator depresses or manipulatesI the wrong` ringing key, the saine can he released. Normally the depressed or manipulated ringing keys are not released until the parties at both the calling and called sub-stations` have re-k placed their respective telephone receivers on their switch-hooks, thereby opening the circuits through the supervisory lamps and consequently opening the circuit through the Winding of magnetic clutch 46.

Should the calling party at sub-station 1, replace his telephone receiver upon its switch-hook, previous to the response oit the called party, the ringing current is at once cut oil' .from the called ,sub-station, and the calledV line is freed for further connections. This action is brought about by the fact that operating current for ringing relay 40 vis furnished through the lowerniost oit the two top larmature switches of ans wering relay 25, in the case of a waiting connection, or through the intermediate one ot' the three bottoni armature switches ofvsaid relay, in

' connection. ln either case, the de-energizationcil answering relay 25, due to the replacing of receiver 2 on switch-hook 4l at substation l, would open the circuit through ri relay 40 which would consequently release its various operated armature and spring switches. As no operating current would therefore loe pass ing through cut-off relay 37, the saine would also be cle-energized and line relay 4&1 vwould be restored to the control ot the euh-stations associated with it.

I have shown at Figure 3 an alternative form of producing the required alternating ringing current for party lines, consisting of strong current of one polarity and weak current of the other polarity. lnterrupters 07 .and 98 Aare counterparts ot interrupters 60 and 70. `l-lowever, they are both connected to one terminal of ringing generator 59, the other terminal being connected to ground.

Brush 99 engages the center ot Athe en posed metallic portion oit interrupter 9"?, when the positive current delivered to said interrupter by generator 59 is at its niarmum. Brush 100 engages the center ot the exposed inetallic portion ci interrupter 98, when the negative current delivered to said interrupter by generator 59 is its inaXi mum. A suitable resistance 10i connects the o by such a combination instead ci the one disclosed in Figure 1, and described hereinhetore.

in Figure i l have illustrated a inodilication of the system illustrated in l-Pigure l. ln this torni, when answering` plug 102 (il`-' im tf: in 'ted in the answering ing cut-oh relay le, (Figure 1) sleeve ol: answering jack 12, sleeve Contact ot answerino` pino 102 (ifigure fi), left hand windingv oi icing supervisory relay 103, normal contact e d spring switch 104i ci answeringl relay 10o, top armature switch and left hand nornial contact oit controlling relay 106, retardation coil 1.0"1M and grounded Icattery 108, completing the circuit to ground. `Retardation coil 10T is et a comparatively high re-` sistance, lont allows enough current to pass to actuate answering supervisory relay 108.

rEhe actuation ot said relay closes anotherV circuit which inay lie traced as iollows: troni ground, through cut-ofi' rel y 1,3, (Figure 1) sleeve of ansa-tering jack 1Q, sleeve ot answering plug 102 (lfigure Ll), contact and engaged armature switch o't answering superrisory relay 1,03, winding ot answering relay 105 and grounded battery 108, conipleti the circuit to ground. Cut-oit relay 13 (rigure l) is actuated by the current :flowing through circuit and removes "ie relay 1% troni connection with the calli .g substation line, as has hereinliecre been described.. The actuation of answering relay 105 closes ka circuit; which may he traced toilowsi from ground, through winding 109 of the repeating coil, spring switch L10 and engaged top armature switch of answering relay 105, ring contact cil answering plug l( 9 rino` spring conta' answering jack l2 (Figure l), sub ation apparatus the calling line (as has been hereinhetcre described), tip spring contact insrfe 'ack 12, tip contact ot answer Figure l right hand winding y rele-v 1.03 and the resistance in multiple relation superi' so l conactsy anc'` engaged c ot answering relay 1 ,cattery 108, cornpleting gronnc.

having established this circuit,

ja a circuit closed which may he traced as ilovfs: oni gro neil through the wind- 1.

spring switch 110eng'ages 'spring switch 10-1 of answering relay and` disengages the saine from its normal contact, thereby opening the circuit through the lett hand winding of answering supervisory relay 1025. However, the armature switch ot' said relay does not disengage its contact, owing to the current flowing through the right hand winding oi the same.

The actuation of answering relay 105 also connects the operator-s telephone s'et to the calling line. A circuit for this connection may be traced as follows: 'from the ring strand of the link connector through engaged spring switches and 1011 of answering relay 105, left y hand normal contact and top armature switch of controlling relay 106, secondary 113 of operator-s induction coil, receiver 114, condenser 112, bottom armature switch and left hand lnormal Contact ot controlling relay 106, where connection is made to the tip strand of the link connector. By means of this circuitthe 'operator and the calling party can converse together. A circuit in branch relation to the described one may be traced from. ground through winding 109 or' the repeating coil, top armature switch `and engaged` spring switches 110 and 104 of answering relay 105, lett hand normal contact and ltop( armature switch ci: controlling` relay 106, retardation coil 107 and grounded battery 108, completing the circuit to ground. Notwithstanding the shunt circuit so foi-ined, on account ot the high resistance of this retardation `coil, there is suiiicient current to operate the substation telephone apparatus and energize the right hand winding oit answering relay 108. Also, on account of the high impedance orn said retardation coil the voice currents passing between the sub-station telephone receiver vand that of the operator, are 'not affected. y Y

Havingbeen told the number of the calling party desires to be connected with, the operator tests the called ior line in the same manner as hasbeen hereinbefore described. 1f the line is busy a circuit nfor the bu's'y test may be traced follows: from tip Contact of calling plug 115, winding 116 of the repeating coil, right andleft hand contacts vo'f the to'p armature switch ofcontrolling relay 106, spring switches 1041 and and top armature switch of answering rel-ay 105, `winding 109 of the repeating coil to ground. Y If the sleeve of the tested jack `is oi' 'a 'potential above that of the earth', current flows through the special test Winding 116 of the repeating coil and as the same is inductive relation' to winding 109, the latteris yaifecte'd not only directly by said 'current but also inductively. Therefore a busy signal is heard in the sub-station receiver and that of the operator. rllhe busy signalmay or may not be oi the character as described in relation to Figure 1, according to whether the described interrupters 24, 415 and 58 are usedl or not.

JW hen calling plug 115 is inserted in a multiplie jack ot a called for line, a circuit is closed which may be traced as follows:` from ground through the winding of cutoi' relay/V37, (Figure 1) sleeve of multiple jack '36, sleeve contact of calling plug 115 (Figure 4), windingl of ringing relay 116', right and lett hand contacts ot the` bottoni armature switch of controlling relay 106, winding 111 of the repeating coil, lett and right hand engaged contacts of the bottom arinature switch of answering relay 105 and grounded battery 108, completing the circuit to ground Due to the lcurrentl liowing through this circuit, the cut-oft relay is actuated, as hereinbefore described, and ringing relay 116 is also actuated. rIhe engagement with its contact of the uppermost one of the two top armature switches of said relay, con-` necting the ring strand ot the link connector to ground through winding 117 ot' the repeating coil. T he engagement of the lower- Inost one of the two top armature switches of said relay with its contact, closes a 'circuit to the live pole ot grounded battery 108, in branch relation to the one from the winding of said relay through winding 111 of the repeating coil. rl`his branch circuit may be traced as follows; treni the upper terminal oi' said winding, lowermost one of the two top armature switches of said relay and its rengaged contact, upper winding of controlling relay 106, normal contact and uppermost one of the two bottom spring'` switches of. calling relay 118, bottom armature switch and engaged right hand yContact 'of answering relay 105, to the live pole of grounded battery 108. Due to the current vflowing through this circuit, controlling relay 106 is actuated and itsarmature switches disengage their respective contacts, thereby removing the operators telephone set romy y association with the link connector, opening the busy test connection to the tip of calling plug 115 and also opening the connection from the upper terrninalroil thewinding of ringing relay 116', through winding 111 oi' the repeating coil to the live pole of groundy ed battery 108. As the described circuit itt through the upper winding' of controlling rev 

